ATLANTA — First lady Michelle Obama debuted on the 2014 campaign trail Monday in Georgia, where Senate candidate Michelle Nunn is working to pick up a key seat for Democrats.

The open Senate seat is a critical battleground in the national fight for control of the Senate, in which Republicans must gain six seats to win the majority. Businessman David Perdue has relentlessly tried to tie Nunn to President Barack Obama, who did not win Georgia in 2008 or 2012.

Mrs. Obama made the trip to boost voter turnout for Nunn among independents, minority and women voters.

“During the 2012 campaign, First lady Michelle Obama was more popular in some states than her husband,” said Tharon Johnson, a Democratic strategist who led Obama’s re-election campaign in the South. “She generates an enormous amount of support from women and will bring the topic of public education to the forefront of campaigns in Georgia.”

To counter the GOP’s efforts, Nunn and other vulnerable Democrats are emphasizing their independence from the president on issues like the Keystone XL oil pipeline and carbon emissions. Nunn, the daughter of veteran Democratic Sen. Sam Nunn, won’t talk about how she would have voted on the president’s signature health care law, sticking instead to what she’d change about it.

“While Michelle Nunn is trying to distance herself from President Obama and Washington Democrats publicly, she clearly has no problem raising money from them directly on the taxpayers dime in order to deceive Georgians about her true allegiance to President Obama and Harry Reid,” said Perdue’s spokeswoman, Megan Whittemore.

Mrs. Obama’s visit is designed to pump up a voter registration effort led by the state party. Georgia Democrats have been hoping that an increase in out-of-state residents and a growing minority population would help them regain power after Republicans claimed every statewide office in 2010.

That year, in a competitive governor’s race, the Democrat lost by about 259,000 votes. Democrats are hoping that by use of targeted voter registration and outreach efforts, including contacting voters who only vote in presidential years, they will be able to make up the difference.